It is desirable to provide a hard diskette cartridge to protect a floppy disk contained within the diskette cartridge. A hard cartridge not only provides greater physical protection for the disk but also causes less drag on the floppy disk when the disk is being rotated.
It is also desirable that a diskette drive designed for a hard cartridge be able to use a soft cartridge as well. The users of hard cartridge diskette drives can then continue to use their present supply of soft diskette cartridges. However, a hard cartridge is much thicker than the conventional soft envelope cartridge. The problem then becomes how to load diskette cartridges of different sizes in a floppy disk drive and how to position them to the spindle that rotates the floppy disk. In other words, both cartridges must be loaded so that the floppy disk is in the same plane of rotation of the spindle.
U.S. Pat. Nos. 3,770,908 and 3,845,502 are examples of floppy disk drives with cartridge carriers that move a cartridge into the spindle plane of rotation after the cartridge is inserted in the drive. However, all cartridges have the same thickness. Therefore, the carriers do not have to bring cartridges of different thicknesses to a position where the flexible disk in each cartridge is in the same predetermined plane of rotation.